New HRM build

[Structo]

I use a 150K and .001uF cap on parallel for my treble bleed circuit.
I like it but on some guitars like my strats I change that a little.
But it depends on the guitar and pickups.

[groovtubin]

I got my ported cabinet today! I'm glad I had one built for me as I don't have the proper wood working equipment to make a good one myslef. Also, I found it difficult to find information on a Dumble style cabinet with the round ports. Internet and forum searches are clouded with hits dealing with the more popular TL806 Thiele cabinet.

In fact while searching I even found an old post from dogears inquiring about the Dumble round-port cabinet:

This [TL806 diagram] is the design for an open port bass reflex cab. It is not the design for the dual tuned port Thiele box than Dumble favored. Maybe someone here has those plans....

So, I had Brandon make a cabinet for me. He knew the design that I wanted and delivered a good product (though I presume someone else made the cabinet for him).

I suspect there are a number of you that also can supply these cabinets. Feel free to post what you have to offer on this thread. I think 'build threads' like this serve as an important source of information for those who are in the planning stages of building an amp (over 8000 views for this thread so far).

[IMG:640:480]http://img.photobucket.com/albums/v670/ ... tsmall.jpg[/img]

EV???? LOVE mine! I`m using a old 2 x12 cab from a Sunn Beta lead amp, sold the amp carcass, and love the cab, just using one EV, Bout afraid ta throw the other one in! lol! AWESOME aint the WORD!!

[ic-racer]

I wish there were a way to A/B test if I'll like the higher voltages, seeing as how a transformer change is a big deal. .

Replying to myself here. I got a Variac that goes to 140V. So I plugged the HRM into it and started spinning the knob and listening. It seems my amp sounded best around 120 volts. I tried to not look at the knob and twist it around a little so I did not know the voltage it was set at. I did this quite a few times and it was pretty consistent near 120 each time.

I want to try it again with my bias probe on it to see how the output tube bias was changing or not changing as I altered the line voltage.

[ic-racer]

Darn Manzamp! It sounds so good, I have to go back to the HRM and start tweaking.
I took the chassis out and hooked up to the Variac and started testing and recording values and playing.

I can't match the voltages exactly to the amp in the "Dumb Bell" notes because my amp has (based on detailed pictures) a different dropping string and different V1 plate resistors. I can get the EL34 plates to match or I can get the V1 plates to match. So, really it is a guessing game to know what the voltages were in the amp I copied.

In case anyone is wondering what happens to the EL34 cathode current when changing the line voltage with the Variac. The plate voltage change has more effect than the bias supply voltage change. So as the Variac increases the line voltage, the bias current goes up. In my case it was like 20ma at 120v changing to 30ma at 140v. It is no big deal to re-bias after each voltage change.

To get 465 VDC at the first node I only need to set the variac to 124v. My line voltage is just about 120v without the variac.

[Reeltarded]

I would be very uncomfortable going over actual 130VAC. Very. I am fairly uncomfortable with some amps at 120, hence my variacs.

[ic-racer]

I would be very uncomfortable going over actual 130VAC. Very. I am fairly uncomfortable with some amps at 120, hence my variacs.

At 140vac input, here are some values:
Plates = 515v
V1 = 221v and 212v
Heater = 7.56vac

[jelle]

Key is keeping the heaters at 6.3v. Above is serious danger zone as the electron cloud at the cathode gets too big and the tube will subsequently overdissipate.

[ChrisM]

I would be very uncomfortable going over actual 130VAC. Very. I am fairly uncomfortable with some amps at 120, hence my variacs.

At 140vac input, here are some values:
Plates = 515v
V1 = 221v and 212v
Heater = 7.56vac

Those numbers make me a bit nervous!

[ic-racer]

I would be very uncomfortable going over actual 130VAC. Very. I am fairly uncomfortable with some amps at 120, hence my variacs.

At 140vac input, here are some values:
Plates = 515v
V1 = 221v and 212v
Heater = 7.56vac

Those numbers make me a bit nervous!

Which values? Realize this was just a temporary listening test to see if I could hear a sonic improvement that would justify a new PT.

EL34 should be good to use full time at 515, though this was just a temporary test.
V1 at 221v was a target voltage
Heater at 7.56 too high? I have never found maximum voltage specs (if they even exist*) I have done my own tests. My tube tester heater voltage goes to 110V! I have run 12ax7 heaters at 12.6v for a few hours. Cranking to 24v turns them into small light bulbs. I'm sure they will have shorter life span, but it is not like they go POOF at that voltage. I did not have any junk EL34s to try.

If you ask me, my main concern prior to the voltage tests was blowing the indicator LED. Those are a pain to wire

*This is from the "Reciever Tube Manual"

The design of elecdtron tubes allows for some variations in the voltage and current supplied the the filament or heater, but most satisfactory results are obtained form operation at the rated values...a high cathode voltage may cause rapid evaporation of cathode material and shorten tube life.

[Reeltarded]

If you don't care I don't care. I have blown stuff up for fun before.

[Structo]

This is a good book by Robert B. Tomer.

"Getting the Most Out of Vacuum Tubes"

He talks a lot about heater voltages and ways to prolong tube life.

[ic-racer]

Structo, thanks for posting that.

The tone on this video is the end product of my 5 years studying Dumble style amps.

Verbrator and Boss delay in effects loop
NOR input
Volume 6
T, M, B (Both OD and PAB engaged for whole clip except short clean section in middle)
Mid off
JAZZ (forgot this is set to JAZZ, so when I go 'clean' in the middle section I can't figure out why it is so quiet , you can see me frantically fiddling with the guitar knobs around 6:00).
Overdrive 6
Overdrive Volume 3

Marshall power brake middle setting.

EV12S cab, close miked into Apple Logic with a tad of stereo reverb.

http://youtu.be/78raAKXpZtI

Oops I see I forgot to flip the video. The computer's built in camera gives a mirror image.

[sepulchre]

Man, that sounds Great! What tone! Excellent playing as well.

[tubedogsmith]

Stucco, thanks for posting that.

The tone on this video is the end product of my 5 years studying Dumble style amps.

Verbrator and Boss delay in effects loop
NOR input
Volume 6
T, M, B (Both OD and PAB engaged for whole clip except short clean section in middle)
Mid off
JAZZ (forgot this is set to JAZZ, so when I go 'clean' in the middle section I can't figure out why it is so quiet , you can see me frantically fiddling with the guitar knobs around 6:00).
Overdrive 6
Overdrive Volume 3

Marshall power brake middle setting.

EV12S cab, close miked into Apple Logic with a tad of stereo reverb.

http://youtu.be/78raAKXpZtI

Oops I see I forgot to flip the video. The computer's built in camera gives a mirror image.

Man, that is a great tone there!!

[Structo]

That sound really good!